I am looking into techniques, tips and processes on how to make casts using either concrete and/or plaster.
would prefer concrete.
thanks for any advice,
H
mdler
May 16, 08 12:42 pm
concrete is heavy....just remember that...
PodZilla
May 16, 08 12:42 pm
Two tips from someone who tried this unsuccessfully last semester:
1. make sure your mold is super watertight. Plaster is just slightly thicker than water and will leak out of even the smallest cracks.
2. If you're going to use plaster, please make sure you buy Hydrocal or similar that's meant for casting. The cheap plaster of paris from Home Depot is extremely temperamental and has an extremely short work window. It'll cost a bit more but it will make your life a lot easier in the long run. Also, make sure it's mixed correctly. If it's too thin, it'll take a year and day to cure. If it's too thick, it won't pour into the mold and will set too quickly.
Good Luck!
xtbl
May 16, 08 1:11 pm
what are you casting? is it for a model?
the couple of times that i did cast stuff in school, i always liked using pour stone. it's a fast-setting anchoring cement. if you build your formwork right it comes out really nice.
but yeah, it's heavy.
snook_dude
May 16, 08 1:12 pm
You need to have a releasing agent which covers the form inwhich your casting. If your doing plaster, you can use "Wisk" the degergent
in the Liquid State. I have used it in casting relief medallions. In casting in plaster you also have to take care not to create bubbles in your plaster by stirring the crap out of it. Never lift your paddle out of the plaster. Lots of luck. Start Small and you will have alot better luck when you need to go big. Actually if you get this down, you can move onto casting Bronze....now that kicks arShe!
binary
May 16, 08 1:14 pm
when i casted some counters for a bathroom this is how i did it
made a24"x24" form with formica for the sides and silicone for the corners.... i used a 3/4" tube and cut it at 45degrees to scrap the wet silicone and create a roundover for the edges
the form was 1.5" deep and i used 4 bars or rebar and 3 layers or drywall mesh
my form was upside down so i could get a smooth finish against the formica and no water marks...
make sure the mold/form is totally level and sturdy
i could barely carry a 24"x24"x1.5" slab..... it was heavy and had to carry it to the 2nd floor...
seal it also if you are using it in a wet condition.....
b
nothere
May 16, 08 1:40 pm
thanks!
treekiller
May 16, 08 3:48 pm
if the plaster casting leaks, throw some (unmixed) plaster powder at the gusher and it will stop leaking.
PodZilla
May 16, 08 3:52 pm
Treekiller, great tip! could have used that a month ago...
treekiller
May 16, 08 3:56 pm
to tint plaster, mix tempra paint or dry pigments into it.
holz.box
May 16, 08 4:02 pm
packing tape makes a killer finish for concrete, fyi.
invisiblecanook
May 16, 08 11:22 pm
If it is a small enough piece, rockite is the way to go. Build your formwork out of bass wood, and use paste wax as a release agent. Works every time. Plus with rockite, you can water it down to the consistency of ganache, and it pours real easy out of a cup.
citrus.grey
May 16, 08 11:51 pm
I agree with the Rockite but I’d build the formwork out of Plexiglas, it's stronger than bass wood, cheaper, water tight, and it doesn't need a releasing agent. Another benefit of a plexi mold is that you can piece it together with a hot glue gun which means it comes apart easily and can be used again and again.
Hi,
I am looking into techniques, tips and processes on how to make casts using either concrete and/or plaster.
would prefer concrete.
thanks for any advice,
H
concrete is heavy....just remember that...
Two tips from someone who tried this unsuccessfully last semester:
1. make sure your mold is super watertight. Plaster is just slightly thicker than water and will leak out of even the smallest cracks.
2. If you're going to use plaster, please make sure you buy Hydrocal or similar that's meant for casting. The cheap plaster of paris from Home Depot is extremely temperamental and has an extremely short work window. It'll cost a bit more but it will make your life a lot easier in the long run. Also, make sure it's mixed correctly. If it's too thin, it'll take a year and day to cure. If it's too thick, it won't pour into the mold and will set too quickly.
Good Luck!
what are you casting? is it for a model?
the couple of times that i did cast stuff in school, i always liked using pour stone. it's a fast-setting anchoring cement. if you build your formwork right it comes out really nice.
but yeah, it's heavy.
You need to have a releasing agent which covers the form inwhich your casting. If your doing plaster, you can use "Wisk" the degergent
in the Liquid State. I have used it in casting relief medallions. In casting in plaster you also have to take care not to create bubbles in your plaster by stirring the crap out of it. Never lift your paddle out of the plaster. Lots of luck. Start Small and you will have alot better luck when you need to go big. Actually if you get this down, you can move onto casting Bronze....now that kicks arShe!
when i casted some counters for a bathroom this is how i did it
made a24"x24" form with formica for the sides and silicone for the corners.... i used a 3/4" tube and cut it at 45degrees to scrap the wet silicone and create a roundover for the edges
the form was 1.5" deep and i used 4 bars or rebar and 3 layers or drywall mesh
my form was upside down so i could get a smooth finish against the formica and no water marks...
make sure the mold/form is totally level and sturdy
i could barely carry a 24"x24"x1.5" slab..... it was heavy and had to carry it to the 2nd floor...
seal it also if you are using it in a wet condition.....
b
thanks!
if the plaster casting leaks, throw some (unmixed) plaster powder at the gusher and it will stop leaking.
Treekiller, great tip! could have used that a month ago...
to tint plaster, mix tempra paint or dry pigments into it.
packing tape makes a killer finish for concrete, fyi.
If it is a small enough piece, rockite is the way to go. Build your formwork out of bass wood, and use paste wax as a release agent. Works every time. Plus with rockite, you can water it down to the consistency of ganache, and it pours real easy out of a cup.
I agree with the Rockite but I’d build the formwork out of Plexiglas, it's stronger than bass wood, cheaper, water tight, and it doesn't need a releasing agent. Another benefit of a plexi mold is that you can piece it together with a hot glue gun which means it comes apart easily and can be used again and again.
دور لامپی پلیمری گروه تولیدی لوگوکات از جنس فوم فشرده میباشد